Pulse oximeter (or pulse-ox) assemblies include sensors that are configured to measure heart beat rate and/or the oxygen saturation of the blood, and are of particular importance in emergency medical situations as well as the monitoring of patients with respiratory or cardiac problems. Generally, pulse oximeters operate by directing light, such as in the red and/or infrared wavelength range, from one or more light emitting diodes (LEDs) toward the skin and blood vessels. In operation, the pulse-ox assembly emits light from the LED(s), and a photodiode collects the light reflected from the subject's body (reflectance pulse oximetry) or transmitted through the subject's body part (transmissive pulse oximetry). Light in the red wavelength range is absorbed at a different rate than the infrared light. Accordingly, the ratio of oxyhemoglobin and deoxyhemoglobin can be calculated from the respective amounts of reflected or transmitted light.
To reduce potential interference, prior art pulse-ox sensors are generally configured to be worn on intrusive portions of the body such as wrists, fingers, or ear lobes. The measured heart rate and blood oxygen saturation of the subject is then reported on a local digital display or transmitted using wireless communication connections (e.g. bluetooth) to a remote display or system.
Adoption and implementation of typical pulse oximetry technology is practical in hospitals or home settings where the subjects are generally sedentary, however under exercise environments, such swimming or diving settings, it may be problematic. For example, blood flow is increased to the muscles that are being worked during exercise, thereby reducing blood flow to the extremities, such as hands, making them cooler. In turn, blood vessels in the extremities may open wider, which may then lead to blood pooling. Accordingly, monitoring SPO2 in the extremities of an exercising subject may lead to inaccurate vital signs readings. And wearing sensors on fingers or wrists is cumbersome during exercise (e.g., swimming) and may become detached through vigorous activities. Moreover, self-monitoring is not practical for those engaged in other cognitive and physical activities.
Therefore, a need exist for new pulse-ox sensor assemblies that overcome one or more of the problems of the prior art.